Bird flu outbreak proves we’re still ‘just flying blind’
Four years into COVID, experts fear we are no better at detecting viruses
Michael Worobey knows where lightning can strike.
That’s because long before he was an evolutionary biologist tracking down the origins of viruses such as HIV and SARS-CoV-2, he was a firefighter in B.C., lowered by helicopter to look for forest fires after lightning strikes — chase the lightning, and you can find the fires before they get out of control.
But four years into COVID, and with bird flu spreading largely undetected in U.S. dairy cattle for months now, he says he’s appalled governments aren’t doing similar surveillance for potential pandemic viruses.
“We know that forest fires are going to happen. And so we make that investment,” said Worobey, a Canadian who is a professor and department head of Ecology and Evolutionary Biology at the University of Arizona.
But with the biological version of a forest fire, “where these viruses can spread like wildfire through animals and people — we’re still basically just flying blind,” said Worobey. And the result, he said, is now “a raging conflagration that is already spread across most of the United States.”
Around the world this year, disease experts like Worobey are focused on the threat of highly pathogenic avian influenza, or bird flu. The H5N1 virus, which has long been singled out for its potential as a threat to humans, may never develop into a global pandemic on the scale of COVID — but, the experts say, governments have so far been too slow to respond to a very real risk.
And even if the next globe-sweeping pathogen is not bird flu, they say, a key lesson of COVID is that the best time to fight a forest fire is before it takes off.
Bird flu in the U.S.
The H5N1 virus wasn’t detected in dairy cattle in the U.S. until March of this year, about four months after Worobey estimates it was first passed from a bird to a single dairy cow, and then spread through the herds.
It took another month for the United States Department of Agriculture to release samples of the virus, which Worobey and his team used to piece together the molecular clock that could tell them the date of that first transmission.
Since the initial discovery, bird flu has since been confirmed in 49 herds in nine states.
The response has been far slower than with COVID, said Worobey. “There was a full genome sequence in COVID within about a day of people realizing in Wuhan that there was probably a new viral epidemic.”
Canada, like the U.S., has been slow to react, said Worobey.
The government announced a month after bird flu was detected in U.S. cows that it would require dairy cattle imported from the U.S. to test negative for the flu. Around the same time, it said it would begin conducting tests of retail milk for viral fragments. (The Canadian Food Inspection Agency announced this week that 142 samples of retail milk tested negative for fragments of bird flu.)
“Canada is certainly no better in terms of preparing in advance for the certainty that there’s going to be outbreaks in animals that could then have pandemic potential,” Worobey said.
In an email, Health Canada said that “based on current scientific evidence, the risk of avian influenza infection to the general public remains low.”
For now, there is no suggestion that bird flu is being spread in cattle by respiratory droplets — an important distinction when identifying its potential for pandemic transmission.
Instead, scientists believe the virus, which is found in greater concentrations in a cow’s udder, is being spread through animals coming in contact with the virus in milking equipment.
The virus causes mastitis, inflammation of the udder, which affects milk production; the milk of infected cows appears curdled and is thrown out. The U.S. Food and Drug Administration (FDA) said in early May that tests confirmed that pasteurization is effective at killing any live virus.
There is a risk, however low, that bird flu can spread to farm workers who touch infected animals, as it did in April in Texas, where a worker’s eye became inflamed due to the virus.
The CDC recommended last week that state health departments in the U.S. work with their agriculture counterparts to make personal protective equipment (PPE) available to workers on dairy farms, poultry farms and in slaughterhouses.
Several infectious disease experts are also calling for the development of more specific vaccines for birds, animals and humans.
Scaling up production of human vaccines against the new H5N1 variants “seems imperative,” a group of researchers wrote in a paper that ran in the April edition of the International Journal of Infectious Diseases, “primarily to protect high-risk individuals such as farm workers against infection, but also for stockpiling, and secondly to increase preparedness should the virus evolve to sustained human-to-human transmission.”
A new variant of a well-known threat
Bird flu is not new.
In the late ’90s, an outbreak in Hong Kong in chickens jumped into humans, infecting 18 people and causing six deaths. In the following years, there have been other small outbreaks with similarly high mortality rates.
In the past couple of years, however, the virus has spread to affect more wild birds than ever before.
It has continued to jump from wild birds to domestic poultry, where it can cause severe disease and death. Millions of chickens and turkeys have been culled to stop the spread of the virus.
And for the first time, the current subvariant of H5N1 has shown a propensity to jump to mammals “and in some cases likely transmit mammal to mammal,” Worobey said — “We’ve seen that in mink. We saw that in sea lions.”
But “we’ve never seen it in something like cattle, which are terrestrial mammals that we have very, very close interactions with, every day, directly and indirectly through their product,” said Worobey.
As of last summer, the virus had affected at least 26 species, according to a statement by the World Health Organization. At the time of the statement, WHO recommended that given the unprecedented spread of the avian influenza virus among birds and mammals, and the potential risk to humans, that countries enhance biosecurity measures on farms, rapidly detect and report animal outbreaks and strengthen influenza surveillance in animals and humans.
Currently, the U.S. has a limited stockpile of H5N1 vaccines that target earlier strains of the virus and were made using traditional eggbased vaccine manufacturing.
Work has already started on mRNA vaccines — first used in COVID — against bird flu at the University of Pennsylvania by Dr. Drew Weissman, a physician and immunologist, who won the Nobel Prize in physiology or medicine for his work on mRNA vaccine research with Katalin Karikó, an adjunct professor of neurosurgery, also at Penn.
The vaccines can take as little as a month to create, said Weissman, compared to nine months for more traditional vaccines. The University of Pennsylvania has been developing mRNA vaccine technology for use in animals for at least seven years and inoculation of cows was expected to begin this week. The work being done is in the research phase and there is no vaccine approved for animals by the United States Department of Agriculture.
Weissman said the goal was eventually to develop an mRNA vaccine against bird flu for humans.
“Certainly for cows, and farm workers who work with the cows, I think they need to be immunized,” said Weissman.
But developing a vaccine takes money.
Weissman said it costs $1.5 million (U.S.) just to make a vaccine and another $700,000 to do a toxicity study to understand elements such as potential adverse effects and safe dosages. That work has to be submitted to the FDA before clinical trials can start.
Canada has two H5N1 pandemic vaccines — authorized before mRNA technology came into use — but they are currently not available.
The vaccine production process in this country is triggered by the World Health Organization.
WHO would have to make a pandemic influenza declaration, or a recommendation that influenza vaccine manufacturers switch from seasonal to pandemic influenza vaccine, before production would start, said Health Canada in an email.
The government has agreements in place with several vaccine manufacturers — domestic and international — to ensure timely access to pandemic influenza vaccines for the entire Canadian population, according to the email, and has proactively met with GSK, the manufacturer that would make the vaccine, as well as other manufacturers, to discuss preparedness activities.
‘‘ Canada is certainly no better in terms of preparing in advance for the certainty that there’s going to be outbreaks in animals that could then have pandemic potential.
MICHAEL WOROBEY BIOLOGY DEPARTMENT HEAD UNIVERSITY OF ARIZONA